Electrolytic cell processes for the production of sodium hydroxide and chlorine from brine are well known in the art. In these processes, alkali is formed at the cathode while chlorine is formed at the anode. Additionally, hydrogen is formed at the cathode. Frequently, the commercial demand for chlorine has been less than the demand for sodium hydroxide which has lead producers to find other uses for the chlorine manufactured. Some have suggested reacting the chlorine gas with hydrogen to form hydrogen chloride gas which is then absorbed in water to form hydrochloric acid. Others have suggested avoiding the production of chlorine by reacting the chloride ions present in the electrolyte with hydrogen ions formed at a hydrogen gas anode forming hydrochloric acid in the liquid electrolyte.
One such patent is U.S. Pat. No. 3,963,592, which discloses a process in which the anodic reaction products can be varied to produce either chlorine or produce hydrogen chloride in the anolyte. The process utilizes an anode which is capable of operating both as a hydrogen anode or as a chlorine anode. When operated as a hydrogen anode, the hydrogen is passed through a first and then second layer of the anode into the anolyte where the hydrogen ions react with the chloride ions to produce hydrochloric acid in the anolyte.
Production of hydrogen chloride in the liquid anolyte may eliminate the step of chlorine production followed by reaction with hydrogen, however, separation of the hydrogen chloride from the brine of the anolyte poses difficult and expensive separation problems, as well as creating problems of low current efficiency.